Sorry for my English. I'm using Firefox 72.0b11 (using 71.0 before, same issue). When I open Firefox and do noting, The Firefox memory usage is slow rising. In Process Explorer, The firefox.exe Working Set memory using looks normal,But Private bytes memory usage is too much. (Please see attach screenshot) I try using about:memory to figure out what's happen, But I can't find problem. Here is memory-report.json.gz from about:memory , Is any idea can definite why using lot of private memory? http://www.mediafire.com/file/vgmt2hs0catu0pp/memory-report.json.gz/file Thank you.